Method of dissolving and recovering rubber.



' UNITED STATES PATENT OFFICE.

GEORGE A. LQOLIFT, WEST BROMWIOH, ENGLAND, ASSIGNOR TO ROBINSONBROTHERS, LIMITED, AN ENGLISH TRADING COMPANY, OF WEST BROMWIOH,ENGLAND. I

Specification of Letters Patent.

Patented. Nov; 28, 1905.

Application filed March 3, 1905. Serial No. 248,324.

To all whom it may concern:

Be it known that I, GEORGE ALBERT LLEW- ELYN OLIFT, chemist, a subjectof the King of Great Britain, residing at 42 Edward street,

West Bromwich, in the. county of Stafford, England, have inventedcertain new and useful Improvements in Methods of Dissolving andRecovering Rubber, of which the following is a specification.

This invention has for its object the application of a discovery I havemade that pyricovery of serviceable rubber. from waste scraps or refusecontaining rubber the rubber material is mixed with the pyridin or abase of the pyridin group in a vessel and the rubber thus dissolved,leaving the impurities undissolved. This part of the process isconveniently carried out by the use of a number of tanks containing thesolvent, into which the material to be dissolved is lowered within acage or basket, first into one tank and then into the next throughoutthe whole series until the whole of the rubber has been dissolved, or bythe use of a number of tanks into each of which material to be dissolvedis lowered within a cage or basket, and into the whole series of whichthe solvent is pumped successively from tank to tank, fresh solvent beinpum ed into the tank of the series whic at t e time contains thenearly-dissolved material and the nearly-spent solvent into the tankwhich at the time contains the fresh material, the solvent passing fromthe first-mentioned to the other tank through the intermediate tanks inwhat is the succession of tanks at the time, these methods of workingdissolving-tanks in series being well understood. When the solventwithin any tank has taken up as much of the rubber as is convenientlypracticable, the solution is separated from any impurities andneutralized With an acid, such as sulfuric, when the rubber separatesout.- The process of dissolving the rubber is quickened by heating thesolvent and maintaining it at as high a temperature, such as about 100centigrade, as will not decompose the rubber, and the heating isconveniently efiected by the aid of steam-coils within the tanks, andthe rocess is further facilitated by agitation, suc as by revolving thebaskets within the tanks, and it is of course advisable to use thematerial to be dissolved in the form of small pieces. The tanks arepreferably closed when at work and are rovided with reflex condensers.

T e solvent may be recovered after having been neutralized by an acid byanyof the well-known methods.

Preferably before, but it might be simulta neously with, theneutralizing of the solution with an acid, as above described, coal-tarbenzol orother naphtha or any of the usual solvents of rubber which areadmissible to be used with bases of the pyridin group which will notinjure the rubber-may be added to v the li uid in the proportion ofaboutfive gallons 0 commercial benzol or the other na htha or solvent to onegallon of the liqui to take up the rubber thrown out by the acid andgive a solution of rubber in the benzol or other naphtha or solvent,which solution se arates out in a distinct layer from the pyri in orbases of the pyridin roup when these have been neutralized wit acid andmay be decanted off therefrom. The addition of the lighter solventfacilitates the separation of the rubber from the pyridin or other baseof that group, and the benzol or lighter solvent may be recovered fromthe rubber by being distilled off therefrom by means of steam or byvacuum distillation or by any other well-known means by which rubber maybe separated from benzol or other naphtha or solvent, and both rubberand lighter solvent be recovered in serviceable form. The solution ofrubber in the coal-tar benzol or other naphthaor solvent, however, isitself useful for many purposes, and the solution of rubber formed bytreating waste or other rubber with pyridin or bases of the pyridingroup may be utilized as such for many purposes, and the inventioncomprises the preparation of such a solution to be used as such by thetreatment of serviceable rubber with pyridin or bases of the pyridingroup.

On theground both of expense and of efliciency it is preferred to useheavy bases as the solvent, according to this invention, for the rubberrather than pyridin or kindred bases alone or mixed together as they imight be.

Instead of throwing out the rubber from its solution in pyridin orkindred bases or heavy bases by means of an acid, 'it may be thrown outby any reagentsuch as woodspirit or amyl alcohol, which when mixed withthe solution of rubber in pyridin or kindred bases or heavy basesdestroys the power which the solvent otherwise has of dissolving rubberand precipitates rubber therefrom. This process, however, is notapplicable when the rubber is to be thrown out of the solution in thepresence of the benzol or other naphtha or solvent.

Having thus described my invention,what I claim, and desire to secure byLetters Patent, is

1. The herein-described method of recovering rubber, which consists infirst dissolving out the rubber with a base of the pyridin group, andthen separating the rubber from such solution with a reagent. I

2. The herein-described method of recovering rubber from waste, whichconsists in first dissolving out the rubber with a base of the pyridingroup, then precipitating the rubber from such solution with a reagent,and then recovering the base by suitable means 3. The herein-describedmethod of forming a solution of rubber in a volatile solvent, whichconsists in first dissolving waste rubber in a base of the pyridingroup, then treating such solution with an acid in the pres ence of thevolatile solvent for the separation of the rubber from the said base andits solution in the said solvent, and then separating off the saidsolvent, with the rubber in solution therein.

In witness whereof I have hereunto signed my name this 22d day ofFebruary, 1905, in the presence of two subscribing witnesses.

GEORGE A. L. CLIFT.

, Witnesses:

ROBERT G. Gnovns, PAUL HUFFNER.

